Hierarchical economic MPC for systems with storage states

Economic model predictive control (EMPC) differs from conventional tracking model predictive control by explicitly incorporating the plant economic cost into the stage cost. One particular class of systems of interest in the deployment of economic MPC are those containing storage devices such as microgrids and hybrid electric vehicles. Such systems may benefit from a two layer control architecture due to the wide range of time-scales that can be exhibited, with the first and second layers comprising a scheduling controller and the EMPC controller respectively. This, in turn, requires an alternative control system formulation since its structure differs from standard economic MPC. This paper proposes an EMPC control algorithm that is suitable for this particular two-layer problem. The proposed control algorithm ensures that feasibility is always maintained, even in the presence of a changing cost function. Existing EMPC theory is extended in order to prove stability of a set of economically optimal steady states, in a finite time setting. The proposed controller is then used in a simulation of a network connected, hybrid solar photovoltaic (PV) / battery system, and demonstrated to provide superior performance to standard EMPC. (C) 2018 Elsevier Ltd. All rights reserved.